This description relates to the field of caps for use in closing and sealing a discharge opening at a container's neck such as that of a liquid container.
Several types of cap are already provided for sealing an opening at a container's neck. The main problem generally encountered is that there is a large variation of dimension of the necks, depending on the method used for making necks (e.g. extrusion blow, extruded blow with compressed neck or injection blow). For reducing number of type of caps and for facilitating cap mounting, manufacturers search to produce the most robust cap as possible. A cap must be able to seal a large variety of neck finishes and design. Also, the cap has to seal the container even if neck's external surface is rough/damaged or the pressure in the container is different than outside. In order to seal properly, the cap has to absorb neck surface defects, dents or scratches due to manufacturing imperfections or handling accidents.
Some molded caps comprise one or more flexible lips made of the same material than the cap with a view to provide a seal. The more lips on a cap the more material is used to manufacture the cap.
Other types of cap comprise a seal gasket located on the inner top of the cap. It is generally a ring-shaped seal which is compressed while the cap is mounted on the neck. For sealing necks having various dimensions, the seal gasket must be voluminous for adapting itself. Usually the seal gasket material is more costly than cap material.
There is therefore a need for improved sealing cap providing a water-tight closure at a lower cost.